In general, there is proposed a heating apparatus as shown in FIG. 1 for pre-heating a reaction gas in the CVD process. That is, the conventional heating apparatus includes a quarts tube 30 through which a reaction gas flows, a line heater 50 wound around the outer circumferential surface of the quarts tube 30, and ceramic balls 40 disposed inside the quarts tube 30.
In this case, the line heater 50 transfers heat to the ceramic balls 40 which in turn supplies the heat to the reaction gas for heating the reaction gas.
However, such a conventional heating apparatus as described above entails a demerit in that its volume increases, and it is difficult to extend the length of the quartz tube 30 and to have a large number of ceramic balls 40 disposed inside the quartz tube 30, which makes it difficult to sufficient heat the reaction gas flowing inside the quartz tube 30.